Screening and identification of epiphytic yeasts with potential for biological control of green mold of citrus fruits

Abstract

Epiphytic yeasts isolated from the surface of citrus fruits, harvested in several orchards in the SoussMassa-Drâa Valley, Agadir, Morocco, were in vivo screened for antagonistic activity against Penicillium digitatum, the causal agent of green mold of citrus. From a total of 245 yeast strains assessed for their biocontrol activity against P. digitatum, fifteen reduced the incidence of disease to less than 50%. The effectiveness of the best selected yeast strains showed that Pichia anomala (YT73), Debaryomyces hansenii (YT22) and Hanseniaspora guilliermondii (YT13) were the most effective, with a reduction of green mold incidence from 65 to *80%, compared to the control. The identification of the fifteen selected yeast strains was carried out through an integrated approach including phenotypic and genotypic (sequencing of D1/D2 domain of 26S rDNA encoding gene) methods. These 15 selected were identified as: H. guilliermondii, D. hansenii, H. uvarum and P. anomala. The study of the dynamics of two of the best strains, H. guilliermondii and D. hansenii, showed that these strains can grow rapidly, by approximately 2 log units, in citrus fruit wounds. Such rapid growth in wounds indicates that these antagonist yeasts are excellent colonizers of citrus wounds and can thrive on citrus fruits as a substrate.

Use of a marine yeast as a biocontrol agent of the novel pathogen Penicillium citrinum on Persian lime

“…In the wounds, yeast growths rapidly, but on intact fruit surfaces the antagonist populations usually diminish to the level of natural epiphytic microflora (Droby et al, 2009;Liu et al, 2013). In these sense, the use of adjuvants like Tween 80 (as surfactant) or dextrose (as nutrient) could be an alternative to a better distribution and maintaining of antagonistic yeast population on carposphere at concentrations suitable for biological control, as previously reported (De Cal et al, 2012;Spadaro and Droby, 2016 (Chalutz and Wilson, 1990;Droby et al, 1999;Taqarort et al, 2008). In a recent study marine D. hansenii was capable to inhibit the mycelial growth of pathogenic fungi of maize (Zea mays L.) (Medina-Córdova et al, 2016).…”

Efficacy assessment of Pichia guilliermondii strain Z1, a new biocontrol agent, against citrus blue mould in Morocco under the influence of temperature and relative humidity

“…It has been reported that the impact of these pathogens on the citrus industry differ from country to country. In Morocco, the losses have been estimated at over 60% and are generally controlled by applying chemical fungicides before or after harvesting (Taqarort et al, 2008). Imazalil, thiabendazole (TBZ) and sodium o-phenylphenol (SOPP) are the most commonly used synthetic chemical compounds in Morocco (Lahlali et al, 2004(Lahlali et al, , 2005 and worldwide to control postharvest mould infections (Lahlali et al, 2009).…”

“…They reported that, among 21 medicinal and aromatic plants tested, Thymus leptobotrys, Cistus villosus, and Peganum harmala plants completely suppressed the growth of P. italicum, P. digitatum and G. candidum in controlled conditions. Taqarort et al (2008) screened three effective epiphytic yeast strains, P. anomala (YT73), Debaryomyces hansenii (YT22) and Hanseniaspora guilliermondii (YT13) against P. digitatum among a collection of 245 strains. The objective of this work was to investigate the effectiveness of epiphytic yeast P. guilliermondii strain Z1, isolated from the surface of healthy orange fruit, as an eventual biocontrol agent (BCA) of citrus blue mould.…”

A new semi-selective agar medium for recovery and enumeration of antagonistic yeast, Pichia guilliermondii strain Z1 from orange fruit surface

“…diseases that affect citrus fruit quality in Mediterranean climates (Lahlali et al, 2004;Palou et al, 2002). In Morocco, the losses have been estimated at over 60% and are generally controlled by applying chemical fungicides before or after harvesting (Lahlali et al, 2004(Lahlali et al, , 2005Taqarort et al, 2008). However, the usual appearance of strains resistant to chemicals, the increased concern for the environment and human health, and public demand for minimal residues have contributed to the development of alternative strategies to substitute the use of synthetic chemicals.…”